Improvement of Injera shelf life through the use of chemical preservatives
AbstractMould spoilage is a serious problem that affects the shelf life of injera, the staple Ethiopian fermented bread. Injera is made from teff (Eragrostis tef) but other cereals may also be used in combination with teff. About two-third of Ethiopian diet consists of injera and it accounts for about two-thirds of the daily protein intake of the Ethiopian population. Injera has a high nutritional value, as it is rich in calcium and iron. Unfortunately, injera has a shelf life of only 3-4 days essentially due to mould spoilage. The use of weak organic acid as preservative is allowed in acidic foods,
primarily as mould inhibitors. In this study, the effect of chemical preservatives such as benzoic acid, sodium benzoate, potassium sorbate and calcium propionate were investigated to prolong shelf life of injera. The preservatives were added immediately before baking at the concentration of 0.1% of benzoic acid, 0.1% sodium benzoate, 0.2% of potassium sorbate, 0.3% of calcium propionate and 0.2% blend of the four as recommended by Food and Drug Administration of USA. Three fungal species: Aspergillus niger, Penicillium sp and Rhizopus sp were found to be responsible for injera spoilage. Penicillium and Rhizopus were more dominant at storage temperature of between 16-200C, while Aspergillus niger was found to be more dominant at higher temperature of 25-320C. Injera samples had a pH and moisture content between 3.38- 3.45 and 62-65%, respectively. Anti-fungal activities of the preservatives investigated significantly prolonged the shelf life of injera for up to12 days. It was found out that the effectiveness of preservation was ranked as sodium benzoate>benzoic acid>potassium sorbate>blend>calcium propionate showing that benzoate and benzoic acid are the most effective. The outcome of the research has a significant implication in food security, energy utilization and a significant reduction in the amount of time used by women to produce injera.
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